Two sided coater

ABSTRACT

Two side coaters and methods of coating paper on both sides are disclosed in which a web of paper to be coated is moved in a generally upward direction in partially wrapped relation to a coating roll, so that one side of the web is in contact with and supported by the roll. This one side of the web is coated by a first coating material which is applied by the coating roll. This coating material is applied to the coating roll by an applicator roll, either directly in which a puddle is formed between the applicator roll and the coating roll, or through transfer from a pair of metering rolls in which the coating puddle is formed between the metering rolls. A second coating, which may be the same as or different from the first coating, is applied by a non-contacting jet fountain coater to an area on the opposite exposed side of the web just ahead of or including the area which is in wrapped relation to the coating roll, and the excess coating is blade doctored, employing the coating roll as a back-up roll for the doctor blade. The .[.blade.].  .Iadd.web .Iaddend.side moves upwardly in view of the operator and is turned for subsequent drying or the like with the blade side up. There are also disclosed arrangements by which the lead-in and lead-out angles of the web may be controlled for the purpose of controlling the angle of contact and degree of wrap of the web with the coating roll. The method further contemplates conventional blade doctoring, bent-blade doctoring, and zero-angle blade doctoring.

RELATED APPLICATIONS

This application is a continuation-in-part of my application Ser. No.921,502, filed July 3, 1978 and now U.S. Pat. No. 4,231,318, and myapplication Ser. No. 34,216, filed Apr. 30, 1979, and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a coating apparatus and method by which a webof paper or the like may be coated on its opposite sides either with thesame or with different coating materials.

Various arrangements have been proposed by which webs may be coatedsimultaneously on both sides with similar or dissimilar coatings. Onesuch arrangement is described and claimed in the above co-pendingapplication Ser. No. 921,502, which discloses a dual blade type ofcoater in which a web of paper is moved upwardly between a pair ofopposed non-contacting fountains and the excess materials are removed bya pair of co-acting doctor blades. The doctor blades are mounted forpivotal movement about a common axis.

It is desirable in some instances to utilize a conventional roll-typeapplicator for applying a coating or sizing material to one side of theweb. One patent which discloses a roll applicator in a two-sided coateris Wallsten, U.S. Pat. No. 3,899,615 issued Aug. 12, 1975. In Wallsten,the web moves in a generally downwardly direction over a coating roll,from which the web receives one coating. The opposite side of the web iscontacted by a coating blade which forms a dam and creates a reservoirabove the blade for a coating material.

Such coaters are difficult to operate for a number of reasons. First,the blade-coated side is moving downwardly away from the coater andtherefore is not presented as the top side for immediate drying orcooling systems. Secondly, the entire amount of the excess coating mustbe controlled by the blade alone, which places a severe demand upon theblade and limits the operator's ability to choose coating weights andweb speeds. Very light .[.coatig.]. .Iadd.coating .Iaddend.weights, oraccurate control of coating weights, is rendered quite difficult.Further, since the paper is exiting the coater in the downwarddirection, it is difficult to provide a good operator vantage point forobserving the coated web as it leaves the blade.

SUMMARY OF THE INVENTION

This invention is directed to two-side coaters which utilize the uniqueadvantages of a jet-type fountain to apply coating to one side of amoving web or sheet of material, and a roll coater to apply the same ora different coating to the opposite side. The sheet moves in a generallyupward direction between a coating roll which also forms a backing rollfor the sheet, while a carefully controlled amount of coating is appliedby a non-contacting jet-type fountain at the opposite side of the web.The excess material on the open side is removed by a blade and the bladeside is then presented as the exposed upper surface for application to adrying or a cooling system.

The two-sided coater of this invention may be used in combination with alead in and/or lead out roll mounted for adjustment or movement about anaxis so that the angle of contact of the web with the coating roll maybe varied and controlled in operation to provide for fine adjustment ofthe coating weight.

In a further arrangement, a plurality of smoothing rolls receive the webexiting from the coater and provide means for changing the web directionwhile smoothing one of the wet coated surfaces.

The coater of this invention has certain advantages. It provides anarrangement by which an existing, blade, roll or transfer roll coatermay be converted into one for coating both sides of a web. It alsoprovides a coater which employs a jet-type fountain and blade coater onone side and differential roll coater on the other side with a web leadexiting the blade in a generally upward direction. The blade coated sideis thus presented up to the drying or the cooling systems. Thearrangement further provides for the varying of the coating weightsindependently to either side of the web. An advantage of the arrangementpermits the conventional coating on one side and the employment of aback side curl control, all at one coating station. The coater may bedesigned to handle very light weight papers with a minimum of web breaksand a minimum of the formation of roll split/film pattern.

The employment of a jet-type fountain applicator for coating of one sideof the web has a further advantage of providing for a wide range ofblade angles from a "zero" angle arrangement in which the blade is heldwith its flat side against the surface of the paper, to a condition inwhich a beveled blade contacts the paper at 55° or more. The fountainapplicator is preferably mounted for both lateral and pivotal adjustmentwith respect to the coating roll, and the blade is also preferablymounted on a support which provides for pivotal movement of the bladeabout an axis which is generally coincidental with the point or regionat which the blade contacts the web.

In many instances it is desirable to apply rather heavy coating weightsto certain kinds of papers. Often this requirement for relatively heavycoating weights, in excess of 10 lbs. per ream, is accompanied by areduction in the viscosity of the coating. Often the typically highviscosity starch systems are replaced by systems in which low viscositylatex is applied to provide an ultrasmooth, high-gloss finish when thepaper is calendered. However, the reduction in coating viscosity fromabout 1500 cps down to 1000 cps for a given web spread results in asubstantial reduction in the hydrodynamic forces at the tip of thebeveled blade, and the result is an unsatisfactorily low coating weight.

In the present invention, the doctor blade may be operated at a lowangle to the web, such as by use of a bent blade or a "zero" angleblade, to permit the metering of higher coat weights. By using ajet-type fountain applicator, a high quality heavy weight coating can beachieved at relatively low speeds, such as down to 100 feet per minuteor lower, while simultaneously applying a sizing coating or a curlcontrol liquid to the opposite side by means of the coating roller. As aresult, the coater is capable of applying 12 lbs. or more per ream atspeeds down to 100 feet per minute or slower, where that may be desired.

The invention is also further directed to a method of coating a paperweb on both sides. The method includes the steps of moving the paper webin a generally upward direction in partially wrapped relation to anelastomer covered coating roll in which a first side of the web ispositioned against or is in contact with the roll, and applying acoating material to this first side by the coating roll. A secondcoating is impinged on the outer or opposite side of the web with anon-contacting coater, at or just ahead of the area where the web wrapsthe coating roll, and the excess coating is blade doctored off byemploying the coating roll as a backing roll for the doctor blade. Themethod further includes the turning of the coated web so as to exposethe blade doctored side up for subsequent drying, and also includes thestep of varying the entrance and/or exit angle of the web of the coatingroll for the purpose of making fine adjustments in the coating pattern.

These and other objects and advantages of the invention will be apparentfrom the following description, the accompanying drawings and theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation, partially diagrammatic, of an offset rollcoater in accordance with this invention;

FIG. 2 is a diagram of a two-roll embodiment of the invention;

FIG. 3 is a diagram showing another arrangement for utilizing thetwo-roll embodiment of FIG. 2;

FIG. 4 shows a modified arrangement of the invention employing a pair ofinclined roll applicators, and in which the fountain is shown as beingpositioned ahead of the wrap of the web on the backing roll;

FIG. 5 illustrates a further adaptation of the two-sided coater of theinvention as applied to a pair of vertical coating rolls;

FIGS. 6-9 illustrate doctor blade arrangements which may be employedwith the present invention; and

FIG. 10 shows an adjustable mounting for the fountain coater in FIGS.1-5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a double-sided coater is illustrated as employing apair of pick-up and metering rolls 10 and 11 which form or define apuddle 12 therebetween for metering a first coating material onto anintermediate applicator roll 14. The applicator roll 14 is, in turn, inrunning engagement with a resilient backing roll 15. A web of paper tobe coated is brought over a guide roll 21 and a tension roll 22 inpartially wrapped relation to the outer surface of the backing roll 15.The web 20 exits in a generally upward direction over a plurality ofdriven smoothing rolls 25, 16, 27 and 28 which turn the direction of webmovement for exit to a dryer. In the place of the smoothing rolls, asingle air flotation roll or a driven chill roll may be employed withthe embodiment of FIG. 1 as described in further detail in connectionwith the embodiments shown in FIGS. 2 and 3. The applicator roll may runat the surface speed of the backing roll down to approximately 5% ofthis speed, while the resilient backing roll 15 may operate at web speedor may be operated at a differential speed to the web, such as plus orminus 5% of web speed, to minimize roll/film split pattern.

Means for applying a second coating to the web includes a noncontactingapplicator in the form of a jet fountain 30. The fountain 30 may be madein accordance with the teachings of Phelps et al, U.S. Pat. No.3,418,970 issued Dec. 31, 1968 or Coghill, U.S. Pat. No. 3,521,602issued July 28, 1970. The fountain applicator 30 is operated innoncontacting relation to the web and causes a transverse, controlledstream of coating material (identified as 31 in FIGS. 2 and 3), whichmay be the same as or different from the coating materials in the puddle12, to impinge against the outer exposed surface of the web 20, eitherat the point where the web comes into contact with the backing roll 15or at a region immediately preceding web contact with the backing roll.With the stream 31 of coating material, adjustable in width, caused toimpinge on the web by the applicator 30 in noncontacting relation withthe web, wrinkles or the like-can pass by the fountain 30. The fountainitself does not introduce any drag on the web 20 and can also produceuncoated dry edges on the blade side.

The amount of applied coating may be carefully controlled at thefountain. The excess coating is removed by the doctor blade 35 upstreamsof the fountain 30. The doctor blade 35 may be supported on a doctorblade assembly as described in Zink, U.S. Pat. No. 3,882,817 issued May13, 1975. The blade 35 is preferably mounted for pivotal adjustment ormovement about a transverse axis, which axis is coincidental orsubstantially coincidental with the transverse region of blade contactwith the web 20. Such a blade assembly mounting relationship, and theapparatus therefor, is described in Coghill, U.S. Pat. No. 3,187,718issued June 8, 1965.

The fountain 30 should also be mounted for lateral and pivotal movementwith respect to the coating roll 15, and FIG. 10 shows a mounting ofthis purpose which is disclosed in the above application Ser. No.921,502. It comprises a pair of generally L-shaped brackets 40 on whichbearings 41 are mounted for sliding movement on brackets 20 by bolts 42in slots 43 in the brackets. The fountain 30 is in turn supported forpivotal movement by shaft 45 journaled in bearings 41, and means areprovided for holding the fountain in any desired position of pivotaladjustment, such as a stop bolt 46 mounted in one of brackets 40.

The web 20 exits or leaves the backing roll 15, which is also the coaterroll for the coating applied on the back side of the web, at an anglewhich is preferably less than the tangent angle of the blade. Theoperator, who will normally be observing the coating operation from thefountain side of the coater, has a clear view of the coated web at theblade side as it passes upwardly over the driven smoothing rolls. Thesmoothing rolls turn with the blade side up for delivery into a dryer orthe like.

The width of coating on either side may be readily adjusted as desired.As noted above the fountain applicator may be restricted as to theeffective width of the die opening to control coating width, in themanner taught in the above-identified Coghill patent, U.S. Pat. No.3,521,602. The roll applicator may be configured to define the width ofcoating applied by the backing roll 15 by suitably undercutting the roll15 and the applicator roll 14 to coincide with the desired coatingwidth. In addition, edge dams or other contacting edge deckles may beemployed for coating width control as disclosed in Schneider et al, U.S.Pat. No. 3,104,182 issued Sept. 17, 1963. Further, it is contemplatedthat full width water sprays may be supplied for each of the coatingrolls in order to assist in starting the coating process and forcleaning up afterward.

An important feature of the method of the present invention resides inthe adjustment of the angle of the doctor blade 35 to run at a minimumof "zero" angle up to 55° or more, as illustrated in FIG. 6, 7 and 8.FIG. 6 illustrates a conventional blade adjustment in which a relativelythin blade 35B of a thickness as small as 0.010 inch or up to 0.025 inchor greater, is brought into contact with the blade doctoring maintainedat the blade tip, and with the adjustment of blade angle being about thecontact region of the blade tip with the web against the backing roll,in the manner taught in the above patent of Coghill, U.S. Pat. No.3,187,718.

It is also contemplated that flexible blade coating may be employed, inthe manner illustrated in FIG. 7, in which an elongated metal orelastomeric blade 35C is urged against the web and is caused to bend inthe direction of web movement, thereby presenting a relatively flatblade surface to the web for applying relatively heavier coatings.

FIG. 8 illustrates the employment of a "zero" angle adjustment for theblade 35D. Thus in FIG. 8, a very small or "flat" blade angle isemployed where it is desired to increase the coating weight evenfurther. This is of particular advantage when operating at relativelylow speed, such as 100 feet per minute. In such an instance, the flatterthe blade the higher will be the coating weight. For all practicalpurposes, the low angle blade approach shown in FIG. 8 can provide asmuch as 1/2 inch of blade contact without causing the blade to bendappreciably.

Since the blade 35, with the jet applicator, does not have to support apuddle or a head of coating, conventional flexible metering rods may beemployed, such as the blade and rod combination 35E as shown in FIG. 9.Typical metering rods are shown in Warner, U.S. Pat. No. 3,084,663issued Apr. 9, 1963 and Barnscheidt et al, U.S. Pat. No. 3,817,208issued June 18, 1974.

FIG. 2 and 3 illustrate further embodiments of the invention andillustrate additional methods by which the invention herein may bepracticed. These embodiments show the employment of the invention with atwo roll-type coater in which the applicator backing roll 15A iselastomer covered and defines a coating puddle 50 with the roll 14A.Roll 14A may operate at web speed down to about 5% of web speed, whileroll 15A may operate substantially at web speed, plus or minus 5%.

In the embodiment of FIG. 2, the web 20 is shown as being broughtbeneath the rolls 14A and 14B and upwardly over the backing roll 15A ina minimum wrapped relation thereto, and exiting in a generally upwarddirection. The fountain applicator 30A is shown as being positionedgenerally at a one-inch gap relation to the web 20 to apply the secondcoating thereto. While the fountain 30A is shown in FIGS. 2 and 3 aspositioned below the region where the web is initially contacts the roll15A, the fountain may be positioned either upstream or downstream ofthis position, as desired, to vary the dwell time of the coating on theweb before coming into contact with the doctor blade 35A. The mostcommon position will be with the jet of coating 31 impinging against anunsupported web as shown in FIGS. 4 and 5.

Again, the coating material applied by the fountain 30A may be the sameas or different from that in the puddle 50. In fact, in manyapplications of the invention, a starch coating may be applied at thepuddle 50 by the roll 15A, while a conventional clay coating or acarbonless type coating may be applied by the jet fountain 30A. Thisincludes the ability to produce CFB in one coating station.

In the embodiment of FIG. 3, the web 20 is shown as being brought overthe roll 15A and through the nip therebetween, and downwardly around thebottom of the roll 15A, in which the puddle 50 is defined by one surfaceof the web 20 and the adjacent surface of the roll 15A. The embodimentsof FIGS. 2 and 3 have particular application to lower speed coaters andprovide a means for converting existing roll coating machines to operatein accordance with the apparatus and method of the present invention.The apparatus and arrangement as shown in FIG. 3 is particularly usefulfor coating relatively heavy webs, such as board and the like, in whicha "size press" effect is achieved within the nip formed between rolls14A and 14B.

The invention further includes means by which the exit angle of the webmay be adjusted as it leaves the backing roll 15 or 15A. For thispurpose a roll 55 is shown as being mounted on an arm 56 for movementabout an axis which is generally transverse to the direction of upwardmovement of the web 20 from the backing roll. As illustrated by thebroken lines in FIG. 2, fine adjustments may be made in the exit or leadangle of the web 20 from the backing roll, which adjustments are usefulin controlling the doctoring effect of the blade 35A. The web leaves theroll 55 with the blade coated side up for delivery to a dryer,substantially as described in connection with the embodiment of FIG. 1.The roll 55 may be a driven chill roll or an air flotation roll.

The embodiments shown in FIGS. 4 and 5 illustrate further arrangementsby which existing roll coaters may be utilized in the practice of thepresent invention. In FIG. 4, an inclined roll coater is shown in whichthe applicator roll 15B is positioned in inclined relation to themetering roll 14B. Again, the web 20 is brought up in engagement withthe roll 15B, with minimum wrap, and the adjustably mounted jetapplicator 30B is shown as applying a quantity of coating along anunsupported length of the web before it comes into engagement with theroll 15B.

FIG. 4 illustrates a further arrangement by which both the lead-in andlead-out rolls may be adjusted to control the extent of angular contactof the web with the applicator roll, both before and after the doctorblade 35B. Thus a lead-in roll 60 may be mounted similarly to the roll55 for limited movement in a direction transverse to the direction ofweb movement, so that movement of the roll 60 as indicated by the arrowsassociated therewith varies the angle of wrap.

The invention is shown in FIG. 5 as applied to a vertical roll coater inwhich the metering roll 14C receives its coating material from anunderlying pan 62 and transfers the same to the applicator roll 15B. Thearrangements of the adjustably mounted fountain 30 and guide roll 60 arethe same as in FIG. 4.

It will thus be seen that the invention provides both method andapparatus for the two side coating of a web of paper, utilizing theadvantages of a conventional roll-type coater on the one hand, andapplying thereto the unique advantages of a non-contacting fountain jetcoater to coat the exposed side, while bringing the web in a generallyvertically upward direction in partially wrapped relation to a coatingroll, for the purpose of presenting the blade side up for easy viewingand subsequent drying. The concept of the invention lends itself to theconversion and utilization of existing roll coater apparatus, by theaddition of a fountain and doctoring blade, to achieve the objects andadvantages of the present invention and to permit coating on both sides.

The invention has particular utility in the application of carbonlesscoating materials, since the coating of different materials on theopposite sides of the web may be accurately controlled by the presentinvention and method, and thereby preventing the intermixing ofdifferent noncompatible coating materials. The invention has theadvantage of providing the ability to apply to both sides of a webeither similar or dissimilar coatings while presenting the blade side upfor drying or cooling systems. It minimizes sheet stress during thesimultaneous application of coating liquids in view of the fact that theweb partially wraps the backing roll at a single coating station.

Thus the coater of this invention can handle and coat extremely lightweight papers with a minimum of web breaks. The smoothing rolls 25-28 ofthe embodiment of FIG. 1 provide a means of changing web direction whilesmoothing the wet coated surface. Similarly, the chill roll 55 of theembodiments of FIGS. 2-5 may also comprise a driven smoothing roll tosmooth the back coated surface, in the manner defined in connection withrolls 25-28, while providing a means for changing web direction topresent the blade side up.

While the methods herein described and the forms of apparatus forcarrying these methods into effect constitute preferred embodiments ofthis invention, it is to be understood that the invention is not limitedto these precise methods and forms of apparatus, and that changes may bemade in either without departing from the scope of the invention.

What is claimed is:
 1. Apparatus for coating a web of paper which isadapted to apply different coating materials to the opposite sides ofthe web in a single pass through the apparatus, comprising:(a) a coatingroll mounted with the axis thereof in fixed position, (b) a fixed guideroll cooperating with said coating roll to maintain an otherwiseunsupported lead-in portion of the web to be coated travelling generallyupwardly from said guide roll to said coating roll, (c) a second guideroll supporting a lead-off portion of the web travelling generallyupwardly from said coating roll and cooperating with said first guideroll to establish the extent of wrap of said coating roll by the web.(d) means mounting at least one of said guide rolls for adjustment withrespect to said coating roll to vary the extent of wrap of said coatingroll by the web, (e) applicator means for applying a metered quantity ofa coating material to said coating roll at a location remote from theportion of said coating roll wrapped by the web for application of suchcoating material by said coating roll to the surface of the web whichcontacts said coating roll, (f) non-contacting coating fountain meanspositioned to direct .[.ametered.]. .Iadd.a metered .Iaddend.quantity ofa coating material against the other surface of said lead-in portion ofthe web, and (g) a doctor blade mounted to engage said other surface ofthe web along the portion thereof wrapping said coating roll to removeexcess quantities of the coating material applied to the web by saidfountain means.
 2. Coating apparatus as defined in claim 1 furthercomprising means for adjusting said fountain means with respect to saidcoating roll to vary the location at which said fountain means.[.applied.]. .Iadd.applies .Iaddend.coating material to the web. 3.Coating apparatus as defined in claim 1 wherein said adjustably mountedguide roll is said first guide roll and said mounting means thereforprovide for varying the path and extent of said lead-in portion of theweb, and further comprising means mounting said fountain means formovement with respect to said coating roll to vary the location at whichsaid fountain means applies coating material to the web. .Iadd. 4.Apparatus for applying a coating to both surfaces of a moving webcomprising in combination:(a) means for advancing the web including acylindrical horizontal back-up roll having a smooth back-up surface forreceiving and supporting a first surface of a web as the web isadvanced, (b) guide roll means spaced away from said back-up roll fordirecting the path of the web to and from said back-up roll andestablishing the degree of wrap of said back-up roll by the web, (c)first applicator means positioned ahead of the location where the webengages said back-up roll for applying a first coating to the surface ofsaid roll so that the coating is transferred to a first surface of theweb in a coating zone, (d) a second applicator means having means forapplying a coating to the second surface of the web in said coating zoneso that the web is coated on both surfaces as it leaves said back-uproll, and (e) means for maintaining the web under tension pressing theweb against said first coating on said back-up roll. .Iaddend. .Iadd.5.Apparatus constructed in accordance with claim 4 for applying coating toboth surfaces of a moving web and further comprising means for adjustingsaid guide roll means with respect to said back-up roll to vary theextent of wrap of said back-up roll by the web. .Iaddend. .Iadd.6.Apparatus constructed in accordance with claim 4 for applying coating toboth surfaces of a moving web:wherein said second applicator means has atrailing blade with the blade in pressure engagement with the web insaid coating zone with means for supplying coating to the web in advanceof the trailing edge of said blade so that the blade smooths the layerof coating on the second surface of the web and the blade pressure aidsin the transfer of coating from the roll to the first surface of theweb. .Iaddend. .Iadd.7. Apparatus constructed in accordance with claim 4for applying coating to both surfaces of a moving web wherein said firstapplicator means applies a sizing to the surface of said back-up roll..Iaddend. .Iadd.8. The method of coating both surfaces of a travelingweb comprising the steps of: (a) guiding the web into engagement with amoving back-up surface, (i b) applying a first coating to said back-upsurface in advance of the location where it is engaged by the web sothat said coating is transferred from said back-up surface to the web,(c) applying a coating to the second surface of the web while it issupported by said back-up surface and substantially simultaneouslyapplying a resilient force to the web to aid in the transfer of thefirst coating from said back-up surface to the web, and (d) driving saidback-up surface at a different speed from that of the traveling web..Iaddend. .Iadd.9. The method of coating both surfaces of a travelingweb comprising the steps:(a) guiding the web into engagement with amoving back-up surface at a predetermined first location thereon, (b)applying a first coating to said back-up surface in advance of thelocation where it is engaged by the web so that said coating istransferred from said back-up surface to the web, (c) pressing the webagainst said coating on said back-up surface only by maintaining the webunder tension during travel thereof from said first location to a secondlocation on said back-up surface, and (d) applying a coating to thesecond surface of the web at said second location and substantiallysimultaneously applying a resilient force to the web to aid in thetransfer of coating from said back-up surface to the web. .Iaddend..Iadd.10. The method of coating both surfaces of a traveling web inaccordance to the steps of claim 9 wherein the application of coating tothe second surface of the web includes the action of a trailing bladewhich applies a resilient force to the second web surface for smoothingthe coating on said second surface and which resiliently forces the webtoward said back-up surface to aid in the transfer of coating from theback-up surface to said first surface of the web..Iaddend.